One thing I found on my first hunt (info wise)....

[Bottomfeeder]

I was in Pro mode at the park, and my detector began to sound funny. sort of a scratchy ongoing static. I thought for a while it was electric, as i was near a pole with a transformer on it.
But, after cutting back on sensitivity and increasing the iron disc to 40, it didn't help.
Then I turned the iron audio on, and there was the answer. the ground was loaded with iron all around me.
But even so, I was picking out several coins.
AT Pro.... I like it.

 

[Mr. Beard]

I had the same thing happen to me the other day. And as you did--turned iron audio on and heard lots of iron grunt noises. It does sound like a scratchy sound. And I still was getting coins from inbetween the trash.

 

[Big Boys Hobbies]

Thanks for sharing! We all need to know this!